Belt buckles for seat belt devices of motor vehicles are generally used to firmly lock a belt latch that is slidably guided on a belt strap or fixedly connected to one end of a belt strap. For this purpose, the belt buckle has an insertion slot for the belt latch and a locking mechanism that can be released via a push button. The locking mechanism is spring-loaded and automatically locks the belt latch on insertion into the insertion slot. To release the belt latch, the occupant pushes down on the push button, thereby releasing the locking mechanism and ejecting the belt latch due to the released spring force of the locking mechanism.
Such belt buckles have long been found in the prior art. One problem of such belt buckles is that the occupant, in order to fasten the belt, needs to find the relatively narrow insertion slot of the belt buckle, into which they will insert the belt latch in order to fasten the seat belt.
DE 39 04 125 A1 discloses providing, on the belt buckle, a light source that is coupled via a light-guiding material to predetermined light emission surfaces of the belt buckle. The light emission surfaces are here the push button itself and an emission surface arranged on a side surface of the insertion slot lying opposite the push button. Because the push button needs to be configured so as to be displaceable in order to function, the light-guiding material fixedly arranged in the push button must be positioned in the push button in such a manner that the light entry surface of the light-guiding material is optically connected to the external light source when the push button is in the non-depressed position. If the light entry surface of the light-guiding material, when in this position, is not optically connected to the external light source due to production-related shape deviations or mechanical influences, then the light either is not passed or only incompletely passed to the push button, so that the push button is not even illuminated, or is illuminated less intensely than was desired.
DE 10 2007 047 704 A1 also discloses providing, in the belt buckle, an optical waveguide having at least two light emission surfaces that are arranged at the ends of the insertion slot. The light emission surfaces themselves are triangle-shaped and are arranged in a free, triangle-shaped surface on the end face of the housing, between the edge of the housing and a conical side surface of the push button. The light emission surfaces are then, in particular, dimensioned so as to fill the free surfaces in the corners of the end face of the housing over as large an area as possible, in order to achieve maximum luminosity.
The present invention addresses the problem of providing an illuminated belt buckle of the generic type, which achieves an especially efficient and uniform illumination of the light emission surface.
An illuminated belt buckle having the features as described herein is proposed as a solution to the problem. Other preferred embodiments of the invention can be found in the drawings, and the accompanying description.